In U.S. Pat. No. 5,694,471, Chen et al. disclose a system for preventing fraudulent use of identity or transaction cards. The cards are chip cards that include an integrated circuit with a unique serial number permanently and unalterably burned into the chip, and having sufficient storage capacity for a card issuer identification (ID) number, user information (name, account number, signature image, etc.), the public key of a public-private key pair, a digital signature, and a personal identification number (PIN) derived from a user password. To initialize a card, a one-way hash function is performed on the issuer ID and user information to obtain a checksum, an XOR operation is performed on the checksum and card serial number to obtain a composite result, and this result is enciphered using the private key of the public-private key pair to obtain the digital signature. Also, the PIN is obtained by enciphering the card serial number using a user-entered password as the key. In carrying out a transaction at a processing terminal, a card is authenticated by deciphering its digital signature using its public key to recover the composite result, performing an XOR operation on the composite result and card serial number to recover the checksum, performing a one-way hash function on the issuer ID and user information to compute a checksum and comparing the recovered and computed checksums, which should match if the card is authentic. The user is authenticated by enciphering the card serial number using a user-entered password as the key to compute a PIN and then comparing it with the stored PIN on the card to determine whether they match.
In U.S. Pat. No. 5,999,626, Mullin et al. disclose a digital signature scheme for a smart card in which signature components for a transaction session are generated partly by the processing chip on the card and partly by the associated transaction terminal. In particular, a signature composed of a pair of elements is generated for a session by comb1ning another pair of elements selected from a set of prestored signing elements on the card, with the initial step in the computation being performed by the processing chip on the card and the result thereof transferred to the transaction device for the additional steps in the derivation. Thus, the identity of the signing elements prestored on the card is not revealed to the transaction terminal, but the bulk of the computation is implemented by the terminal instead of by the processing chip on the card.
These examples illustrate some of the ways in which secure transactions may be carried out when using a smart card, which has an embedded microprocessor chip in it. Thus, a smart card can encrypt and decrypt data (or share part of the computation with another device), that is saved internally in its memory.
In contrast, passive storage media, such as optical memory cards (OMCs), memory chip cards, compact disks (CD-R and CD-RW), or magnetic media, don't have a microprocessor chip. While they have large memory capacity useful for storing complete transaction records, they have not been deemed sufficiently secure for transaction applications like e-commerce. Any transaction system involving passive media will, like those involving smart cards, require card and user authentication protocols, and also will certainly need to have its stored transaction data be encrypted. Some computers already have encryption and protocol control processors inside the hardware, and some IC-chip readers already have some protocol control processors inside them. But in a system using passive storage media, software/firmware protocols and encryption of the data stored on the media will not be enough to ensure adequate security. Other system security components will be needed to prevent interception of decrypted data at any weak link in the transaction system and access to the encryption/decryption keys will need to be denied to all but authorized persons. To date, such security measures have been unavailable to systems that use passive storage media and, thus, in comparison to smart cards the passive media systems have been deemed too insecure for those transactions which are vulnerable to fraud or forgery (e.g., financial transactions.)
It is an object of the present invention to provide data security methods and systems for achieving secure transactions when using passive storage media, such as optical memory cards.
It is another object of the present invention to provide both hardware and software/firmware security measures to deny unauthorized access to cryptographic keys and to prevent interception of decrypted data streams.